Sen. Maria Cantwell, D-Wash., worked on a proposal modeled after a system in her home state that supporters say has realized significant savings. Federal subsidies ticketed for lower-income uninsured would flow to the states, which would negotiate with private insurers to provide coverage for the target population.

Aides said the proposal would be designed to provide coverage for about three-quarters of the nation's uninsured.

Inside the committee, Sen. Bill Nelson, D-Fla., won approval of a change to shield seniors from the impact of a tax increase in the bill for individuals and families seeking to exclude certain medical expenses from their income. Under current law, taxpayers who itemize their deductions are permitted to escape taxes on health costs that exceed 7.5 percent of their adjusted gross income.

Baucus' legislation would raise the threshold to 10 percent, but on a vote of 14-9, Nelson succeeded in returning it to 7.5 percent for taxpayers age 65 and over.

Moments later, Sen. Jon Kyl of Arizona sought to give younger taxpayers the same break, but his proposal failed, also on a vote of 14-9.

It was one in a string of futile Republican attempts to reshape the legislation by inserting stronger anti-abortion provisions and require photo identification to prove eligibility for benefits under federal health programs for the poor. Attempts to kill fees on health industry providers also failed, along party lines, after Baucus said the result would be to wipe out a key source of funds for the expansion of insurance.

Sen. Orrin Hatch, R-Utah, argued that provisions already in the bill to restrict federal funding for abortions needed to be tightened to guarantee they would be ironclad. He said his goal was to incorporate the restrictions into law, "so we don't have to go through it every year."

In recent years, Congress has prohibited federal funding for most abortions through annual spending bills, and Hatch's proposal would have eliminated the need for those yearly votes.

But abortion rights supporters said the proposal would have expanded the current restrictions, and could deny coverage for abortions to working women signing up for coverage through private plans.

Its approval would be a "poison pill ... if it is hung on this legislation," said Sen. Maria Cantwell, D-Wash.

The committee also rejected a proposal from Hatch to strengthen existing legal protections for health care professionals who refuse to perform abortions or other procedures on grounds of moral or religious objections.

Both failed on nearly party line votes of 13-10, with Snowe siding with most Democrats in opposition, and Kent Conrad, D-N.D., voting with Hatch.

Republicans also failed in attempts to require applicants for federal health programs to furnish photo identification as proof of eligibility, an issue that dealt with illegal immigrants. Sen. Charles Grassley, R-Iowa, said the goal was to prevent fraud, but Bob Menendez, D-N.J., objected that the proposals went beyond a required birth certificate required as proof of citizenship.